Artificially Designed Compositionally Graded Sr-Doped NaTaO3Single-Crystalline Thin Films and the Dynamics of Their Photoexcited Electron-Hole Pairs

Rio Konno, Shingo Maruyama, Takumu Kosaka, Ryuzi Katoh, Ryota Takahashi, Hiroshi Kumigashira, Nobuyuki Ichikuni, Hiroshi Onishi, Yuji Matsumoto

Research output: Contribution to journalArticlepeer-review

Abstract

Sr-doped NaTaO3 (NTO) single-crystalline films with different Sr compositions of up to 20 mol %, including an NTO film, were first fabricated on LaAlO3(001) substrates by pulsed laser deposition. A gradual simultaneous increase of the lattice constants and the optical absorption edge energy was found as the doped Sr composition increased, seemingly exhibiting a structural discontinuity at a critical doping level of around 10 mol %. Extended X-ray absorption fine structure (EXAFS) analysis revealed that the doped Sr atoms were substituted for both the A and B sites, with their stoichiometric number ratio close to that previously reported for bulk Sr-doped NTO samples, resulting in the Sr-doped NTO films being still highly insulative comparable to the NTO film. Second, in spite of the well-known intrinsic nature of the high diffusivity of Sr ions in oxides, the compositionally graded Sr-doped NTO films were successfully fabricated almost as designed to have the upward and downward Sr composition gradients with a maximum doping level of 10 mol % from the substrate along the growth direction within the films. The preliminary time-resolved microwave conductivity measurement demonstrated that the lifetime of the photoexcited carriers in the compositionally graded Sr-doped NTO films was longer than in any of the NTO and homogeneous Sr-doped NTO films.

Original languageEnglish
Pages (from-to)226-233
Number of pages8
JournalChemistry of Materials
Volume33
Issue number1
DOIs
Publication statusPublished - 2021 Jan 12

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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